The purpose of this article is to present a rare case of epidermoid cyst of the outer ear in a 38-year-old male patient. During clinical examination, a soft, cystic, globular, and non-tender swelling with restricted motility and well-defined margins was seen in the retroauricular region. Skin over the swelling was normal and not attached to it. The chosen treatment was total surgical removal. The histopathological findings confirmed the diagnosis of epidermoid cyst, characterized by presence of cyst cavity lined by stratified squamous epithelium with orthokeratin production. The lumen was filled with keratin. The connective tissue capsule consisted of fibrocellular stroma with numerous endothelial lined blood capillaries, which were engorged with red blood cells. The proposed treatment was considered successful, as there was no recurrence.

Keywords: Developmental cyst, Epidermoid cyst, Retroauricular

How to cite this article:Dive AM, Khandekar S, Moharil R, Deshmukh S. Epidermoid cyst of the outer ear: A case report and review of literature. Indian J Otol 2012;18:34-7

Cyst is defined as "a pathological cavity having fluid, semifluid, or gaseous contents and which is not created by the accumulation of pus." Kramer (1974).

Epidermoid cyst is a developmental cyst of head and neck. [1] It is also called as epidermal cyst, epithelial cyst, keratin cyst, sebaceous cyst, milia, or epidermal inclusion cyst. [2] Epidermal inclusion cysts are the result of implantation of epidermal elements and its subsequent cystic transformation. The term epidermoid cyst is used in general context in that, irrespective of source of the epithelium, the term persists. Milia merely represent miniature epidermoid cysts. [2] The term sebaceous cyst sometimes is used mistakenly as a synonym for both the epidermoid cyst and another cyst of the scalp known as a pilar, tricholemmal, or isthmus - catagen cyst. However, because both the epidermoid cyst and pilar cyst are derived from the hair follicle rather than the sebaceous gland, the term sebaceous cyst should be avoided. [2],[3]

Epidermoid cysts account for approximately 80% of follicular cysts of the skin and are most common in acne-prone areas of the head, neck, and back. [3] Clinically, the most common site of occurrence for oral lesions is floor of the mouth and may also occur on the tongue, lips, or the interior of the bone. [1],[2],[4],[5] The most common site for head and neck lesions is the lateral aspect of the eyebrows. [1]

Report of cases in the postauricular regions are very uncommon. [6],[7],[8] Epidermoid cyst can occur at any time in life, but they are most common in 3 rd and 4 th decade of life, unless they are associated with Gardner's syndrome. It has got a slight male predilection. [1],[2],[3]

Clinically, epidermoid cysts are present as nodular, fluctuant subcutaneous lesions that may or may not be associated with inflammation. [3] They are slow to progress and remain asymptomatic until or unless secondarily infected. The occurrence of secondary malignancies of types basal cell carcinoma, Bowen disease, squamous cell carcinoma, and even mycosis fungoides, have been reported albeit rarely. [2]

Histologically, cystic lining is comprised of stratified squamous epithelium resembling epidermis. [1],[2],[3] Occasional cases may have areas of pseudostratified ciliated columnar epithelium. [1] A well-developed granular cell layer is seen, and the lumen is filled with degenerating orthokeratin. [3] Dystrophic calcification and reactive foreign body reaction are seen associated with the cystic capsule. Malignant transformation of the cystic lining is noticed not infrequently. Pigmented epidermoid cysts may demonstrate melanin pigment in the wall and a keratin mass. A surrounding infiltrate of melanocytes and macrophages may also be observed. [2]

Treatment of epidermoid cyst includes conservative surgical excision, and recurrence is rare. [1],[2],[3],[4]

In this article, we present a case of epidermoid cyst of the retroauricular region and focus on the review of clinico-pathologic features and biologic behavior.

Case Report

A 38-year-old male patient presented with a prominent swelling behind the right ear since the age of 10 years [Figure 1]. Swelling was initially of peanut size and increased gradually to present size of approximately 3 cm × 3 cm. The swelling was soft, cystic, globular, and non-tender with restricted motility. Margins were well defined. Skin over the swelling was normal and not attached to it. There was no discharging sinus or pointing abscess. Bruit or any pulsations were absent. There was no history trauma, fever, loss of appetite, discharging ear, difficulty in hearing, etc. The patient had no other complaints or other constitutional symptoms. There was no history of such lesions in his family members.

Histopathological examination confirmed the diagnosis of epidermoid cyst by presence of cystic lumen lined by stratified squamous epithelium with orthokeratin production. The lumen was filled with keratin [Figure 4]a and b. The connective tissue capsule consisted of fibrocellular stroma with numerous endothelial lined blood capillaries, which were engorged with RBCs.

The patient was followed up during the next 6 months, and no recurrence of the lesion was observed.

Discussion

Epidermoid cyst is the rare developmental non-odontogenic cyst of head and neck region. [1],[4] Epidermoid cysts of outer ear are rare. [6] There are three cases of retroauricular epidermoid cyst described in literature and five in the Japanese literature. [6],[7],[8]

There is a slight male predilection, and the lesion occurs mostly in middle-aged patients, and our case report of a middle age male patient collaborates with what has been reported in the literature.

The origin of epidermoid cyst is varied. They may form by the sequestration and implantation of epidermal rest during embryonal period, occlusion of the pilosebaceous unit, or iatrogenic or surgical implantation of epithelium into the jaw mesenchyme. Human papilloma virus infection and eccrine duct occlusion may be additional factors in the development of palmoplantar epidermoid cysts. Epidermoid cysts result from the proliferation of epidermal cells within a circumscribed space of the dermis. They have been shown to not be of sebaceous origin based on the analysis of their lipid pattern, which demonstrates similarities to the epidermis. In addition, epidermoid cysts express cytokeratin 1 and 10, which are constituents of the suprabasal layers of the epidermis. The source of epidermis is often the infundibulum of the hair follicle. Inflammation is in part mediated by the horny material contained in epidermoid cysts. Extracts of this material have been shown to be chemotactic for polymorphonucleocytes.

Histologically, the present case consisted of features of epidermoid cyst like presence of cystic lumen lined by stratified squamous epithelium with orthokeratin production. The lumen was filled with keratin. The connective tissue capsule consisted of fibrocellular stroma with numerous endothelial lined blood capillaries, which were engorged with RBCs. [1],[2]

Epidermoid present in the retroauricular region should be differentiated from lipoma and hemangioma. [6] Lipomas are benign tumor composed of fatty tissue and can present the same aspect of the epidermoid cysts. [6],[9] Hemangiomas are often present at birth; they are benign tumors of the vascular endothelia, which can develop in spontaneous manner. [6],[10]

Certain hereditary syndromes have epidermoid cysts as a part of their feature; examples include Gardner syndrome, basal cell nevus syndrome, and panchyonchia congenital. [2]

Treatment of choice is surgical removal and recurrence is seldom noticed. [1],[2],[3],[4],[6]

An unusual complication reported from an oral epidermoid cyst in oral cavity was sialadenitis due to pressure on the submandibular salivary duct. [2]

The present case underwent surgical removal of the lesion, and its success was confirmed by lack of postsurgical alterations and no recurrence of the lesion.